Telephone system



Feb. 3, 1925. 1,524,900

G. A. YANOCHOWSKI TELEPHONE SYSTEM Original Filed Sept. 9, 1921 Patented Feb. 3, 1925.

enoncn A. YANOCHOWSKI, on CHICAGO, ILLINOIS, ns srenon-rorgnnngee BOARD AND SUPPLY COMPANY, on CHICAGO; ILLINOIS, A COREORAfl I'N-- 0F ELINOIS.

TELEPHONE SYSTEM.

Application filedsoptember 9, 1921, Serial No.499,4=22, Renewed s epte rnber is, .1924.

To all whom 225 may concern:

Be it known that I, GEORGE A Ynlvor,

oHoWsm, acitizen of the United States of ,America, resident of Chicago, in the co untyof Cookand State of Illinois, have invented certain new and, useful Improvements in. Telephone Systems, of which the following is a specification.

My invention relates to telephone systems and has to do more particularly with systems of; this type in which impulses transmitted from a calling substationactuate relays to select the contacts of the line being called. The system which is herein dis-v closed is particularly,applicable to private branch exchange systems, and commonly known in the art as a private automatic exchange, althoughmy invention is in no sense limited to, such use.

so A system of the type as above described does away, with;the usual operator .used in manual private branch. exchanges, and an object of my invention is the provision of an improved circuit arrangement which embodies desirable teatures and advantages, all in an eflicient, simplefland economical manner.

A feature of my invention is the provision of a plurality of counting relays, cera called subscriber by. means of a predetermined number of impulses transmitted from a calling, substation.

The above features as well as other novel with a pair of -line, relays LR and LR which relays are energized when the branch exrelays LR andrLR are also influenced by the interruptions of the calllng devlceat the calllng substation A when-transmitting a predetermlned number of impulsesto extain of whiclrrelaysare actuated to select.

change subscriber A initiates a call. The

tend his line. to that of another substationconnected. to, the branch exchange; A ..cut olf relay CO is also. associated .with the calling line and is energized when the line of substation A. is seized as a .calledline, and when inanidle condition as willl lbe more fully hereinafterdescribed. A slow acting on ol re y. hant-1 a l wias ns relay 12 are provided and. areunder the conl o th ner l -ys L a LR; A Swi ing relay SW an d a counting or,.c on necting relay CR are also .provided,, and control the selection of a called line accordingto a predetermined number otimpulsestransmitted from a calling substation. relay TE is also provided which 'is eners, gized or remains'in its -de-energiaed condition depending upon the idle or-busy condition oftlie calledlinetested as saichrelay TE is slightly slow. to. energize due, to its construction andthe arrangement of its.

armatures. A busybacksi'gnallBB isassociated with, the test relay TE, and tran'sniits a busy signal to thecalling line in theevent that the called line is, busy, either, as a calling or calledline. A 'linkcontrolrelay LC isalso provided which is energized when a called line is idle toclose,the continuity of the talking conductors, and asri nging control relay RC is alsoprovided which controls the application of ringing current to the called line. A supervis,ory,relay. ,SR is also provided which energizes when the called party responds to disconnect therings ing current from the called line.

'At B, C, D and E I showdines which terminate in substations similar to Apa nd associated with each substation",Ilillustrate just sufficient apparatus to clearly, describe how a connection may. be extended fromsa calling line toa called line. Eaclrsubstation is provided with relays CR andSVV for each other substation.that that.substation has access to. From this it .will. be

seen that each subscribers line .ismultiplied to relay contacts ot the relays of eaclrother; subscriber that has access to-that particular subscribers line.

Assuming now that thepr vate automatic exchange subscrlber atsubstation A initiates a call, the removal of, the receiver atthesaid substation A closes an energizingwo rcu t for the line relays LR and LE -tracedfrom ground throughthe.winding of the relay A test' LR, conductor 2, normal contact 3, of the cut oil relay CO, through the closed contacts at the substation switchhook, back through normal contact 4 of the cut oil relay CO, conductor 5 to battery through the winding of the relay LR. The relay LR upon energization closes its alternate contact 6, establishing an energizing circuit for the slowacting control relay CL, traced from battery through the winding of the relay CL,

conductor 8 to ground at alternate contact 6 of the relay LR.

The closing of alternate contact 9 of the relay CL places a busy ground upon the common conductor 10 so that should any other substation of the branch exchange attempt to call the calling subscriber A, the line will indicate busy.

Assuming now that it is subscriber C that is Wanted, and assuming that his call number is 2, the private automatic branch exchange subscriber at substation A operates the calling device CD to send two impulses of current causing two interruptions of the impulse springs of the callin device CD causing line relays LR and Iii to be deenergized and energized twice. The first interruption of the impulse spring contacts of the calling device CD brings about the de-energization of the line relay LR and the line relay LR, and the closing of nor-- mal contact 11 of the now de-energized relay LR establishes an energizing circuit for the slow-acting relay 12, traced from battery through the alternate contact 13 of the relay CL, conductor 14 through the winding of the relay 12, conductor 15 to ground at normal contact 11 of the relay LR. The closing of normal contact 16 ol the line relay LR establishes an energizing circuit for the connecting relay CR traced from battery through the upper winding 17 of the relay CR, conductor 18, normal contact 19 of the switching relay SW, conductor 21, alternate contact 22 of the relay CL to round at normal contact 16. The relay C upon energization closes its alternate contact 23 establishing a locking circuit for the said relay CR traced from battery through the lower winding 24 of relay CR, alternate contact 23, con-' ductor 25, normal contact 26 of the relay CR, conductor 27, normal contact 28 of the relay CR conductor 29, normal contact 30 of the relay CR conductor 31 to ground at alternate contact 32 of the relay CL. The closing of alternate contact 33 of the relay CR establishes an energiz ing circuit for the relay SW, traced from ground at alternate contact 34 of the re lay 12, conductors 35 and 36, alternate con tact 33 of the relay CR, conductor 37 throiwh the winding of the switching relay s W, conductor 18 to battery through the upper winding 17 of the relay CR. Relay SYV does not energize at this time due to the fact that its winding is shunted out by the grounded impulse upon conductor 21; as soon, however, as the line relay LR energizes the shunt is removed and relay SW energizes in series with relay CR. Relay Sl V energizing connects the impulse conductor 21 through to the next relay CR. It will. thus be seen that itlakes a de-energization and an energization of the impulse relay to operate one of the counting relays and the switching relay to extend the impulse conductor through to the next counting relay. After the first impulse, of the calling device CD, line relays LR and LR are again energized over the calling line. The relay CL due to its slow to release construction remains energized during the sending of impulses and it ,is not allected by the rapid interruptions of the alternate contact 6 of the a relay LR. The relay 12 is energized upon the first de-energization of relay LR and remains energized during the sending of impulses due to its slow to release construction, and it is therefore not affected by the rapid interruptions of the contact 11 of the relay LR. The relay SW and relay CR when. energized remain energized. dur ing the sending of impulses due to the slow to release construction of relay 12, which remains energized during the sending of the impulse from the calling substation over a circuit as previously described. The next impulse sent from the calling substa tion again opens the energizing circuits of the line relays LR and LR, and the closing of normal contact 16 establishes an energizing circuit for the connecting relay CR from battery through the winding 40 of the relay CR, the conductor 46, normal contact 42 of the switching relay SW, conductor 43, alternate contact 19 of the re lay S l/V, conductor 21, through alternate contact 22 of the relay CL, to ground at normal contact 16 of the relay LR. The closing of alternate contact 26 ot' the re lay CR establishes a second energizing circuit for the relay CR through its lower winding 44 traced from battery through the winding 44, alternate contact 26, conductor 27, normal contact 28 of relay CR conductor 29, normal contact 30 of the re lay CR conductor 31 to ground at alternate contact 32 ot the relay CL. The opening of normal contact 26 of the relay CR opens the energizing circuit of the relay CR through its winding 24, but the relay CR remains energized through its winding 17, through relays SW to ground at alternate contact 34 of relay 12. The closing of alternate contact 45 of the relay CR establishes an energizing circuit for the switch relay SW traced from battery through the winding 40 of the relay CR. conductor 46, through the winding of the llltl switch relay SW, conductor 47, alternate contact 145 of 2 the relay 'GR v, conductors -18 and '35 toground atcalternate contactw34 of the relay 152,11. Relay SVW and CR1 op erate as-before: mentioned tor relays: SW

and CR; For each impulse-transmitted by the calling. device. a2 relay SW and i a re'lay CR"Wlll beoperatedtt Vvhile lihave shown" only 'four: sets zoficountingxrelays; it is ap- I parent that the numberotirelays SW and CRw-iwill depend iupon theisizerot the-:P. B

X., that is, upon the number not substations;

restores. of relayC'R" is alsoopened atwcontaet 3&5 but the relay" CR through its :WindingAA- :toxgrounch at alternate contact 3210f relayCLi -v From the-ioregoingJit::Will be seen that the de-energizati'onof :relay 122permits the. de-energization of 5 all relays .SVVT and CR' l except the last relay GR to'be operated," which connects the desired su bscribers f-line' tothe calling tsubsc-riber7s lineal The closing; of alternate contact 6 of the relay LRfinow holdswthe slow release relay CL permanently energized through: the winding of thesaidn'elayCL to battery.

actuate the: call signal at 'the; 1called-' for substation C, and assuming:-.:tha:t thesub' scriber thereat is idle, ringing current 'W-rlli' be transmitted'to thesaid called 'substation as vwill now be. described. The depression of the ringing keywR-lfat the callingwsubstation A simultaneously grounds-both sides of the linerandthe ground fromithe-alter-l lay LR, permits: therl-inezirelay LR to remain energized; The ground which extends through the normal contact' 3 of thecut ott'relay CO extends through the winding oi-the line relay :LE to ground,"and thisground to ground connectionthrough-the Winding of the line relay LR- permits the same to. tie-energize thus closing .an ener-' gizing circuit for-thecutoit relayTCOas sociated with the idle substation' C, Which circuit may be tracedwfro'm' batterfyvthrough remains energized The party at thesubstation A having transmitted the proper number of impulses to select'the substation C, now: depresses the ringing key RKzatthesuIbstat-i'on-ito the Winding-20f thecutoff relay' Co .con'- ductor '50, alternate contact 51, of therelay CR, conductor 52, normal cont-act'ti of'the relay CR, conductor'54; through the wind' ing of the-test relay TE, conductor 55; normal contact 56 'of the" relay 12 'condu'c t0r=57, to ground at normal contactf58"of the now tie-ener ized line relay LR: The cut off relay C 2 and the test relay TE" are energized over this circuit, and-the-tes't relay TE upon energization closes it'salternate contact 60" establishing a locking circuit for the cut off relay CO and-the test relay TE-tracedfrom battery through the'winding of the cutwofi relayCO conductor 50,"alternate-contact 51 of therelay CR; conductor 52, normalcontact '53 of the relay CR, conductor 54 and through' the" Windingof'the relay TE to -ground atit's" alternate contact 60, the said relays remaining energized until conversation is termi nated'.

The closing'of alternate contact 61 of the testrelay'TE establishes an energizing-ch cuit: for the link connectingcrelayLC traced from battery through the Windingpf the relayLC, conductor 62 to ground at alternate contact 61 of the rela y TE The 'clos ingwof normal contact 63 of 'the lin'e relay' LR establishes an ene-rgizingcircuitfor the ringing control relay RC, traced from batteryat: alternate contact Gtot the -'relay LR, conductor 65-through thewvinding of the relay'RC', conductor 66; alternate con tact 67 of relay TE;-conductor'68'toground at normal contact 63 of line=relayyLlt- The link connecting rela'y LG upon energiza tioir closes its alternate "contacts'69 and 70 to close the continuity of the talking conductors through to the called substation C,

and the: closing of" alternate contacts'Wl and 72 01? the ringing contro-lwcla-y RG' connects the ringing generator Geoas to transmit: ringing current to the called line,"

the 'ringing L circuit being traced from one pole of the generator G, through no-rmal contact 73 of thesupervisory relay 'SRrcoir 'du'ctor 74L, alternate contact 71 ot tlie 'relay RC, alternate contact69 of "the relay LC;

normal contact 75 ot' the connecting relay 78 of the relayCR', conductor 79, 'norni-al contact 80"oI" the-i-elay'Clifalteinatecon 1 tact-70 ofi'elay LG, alternate contact- 72'of the relay RC, normal contact 81 of the supervisoryrelay SR to-theother pole of relay RU closes its alternate- -co1it'a'cts 71 1130' and 72 connecting the ringing generator G through to the called substation C. Upon the response of the called substation C and during a non-ringing period, the supervisory relay SR is energized, traced from battery through the upper winding of the relay SR, normal contact 72 of the relay RC, alternate contact of the relay LC, normal contact of the relay CR, conductor 79, alternate contact 78 of the relay CR, through the now closed contacts at the substation switch hook back through the alternate contact 77 of relay CR, conductor 76, normal contact 75 of relay CR, alternate contact 69 of the relay LC, normal contact 71 oi the relay RC, through the lower winding of the relay SE to ground. The supervisory relay SR is energized over this circuit, and further depressions of the ringing key PK at the calling substation A does not further atfect the ringing circuit as the supervisory relay SR is now energized and its normal contacts 7 3 and 81 are open preventing further application of ringing current from the generator G.

The subscriber at the substation A and the subscriber at the substation C are now in conversational circuit, the said talking circuit now being traced over the heavily marked conductors. After the subscribers have finished conversation they replace their receivers upon the respective switch hooks, and the replacing of the receiver at the sul station A opens the energizing circuit of the line relays LR and LR. The line relay LR upon de-energization opens its alternate contact 6, allowing the slow relay CL to restore to normal. The relay CL restoring to normal, its alternate contact 32 is opened, opening the energizing circuit of the connecting relay CR, and the relay CR now restores to normal. The relay CR restoring, its alternate contact 51 is opened to open the series locking circuit through the cut off relay CO and the test relay TE. The cut oil relay CO and test relay TE are (lo-energized due to the opening of said alternate contact 51 and now restore to normal.

The opening of alternate contact 61 of the relay TE opens the energizing circu t of the link connecting relay LC, which relay now restores to normal. The supervisory relay SR also restores to normal when the subscriber at the called substation C replaced his receiver upon the switch hook.

The apparatus used in establishing the connection between the substation A and the substation C is now at normal and available for use in establishing other connections.

Assuming now that the called substation C is busy, the operation of the circuit is the same as previously described up to the time that the subscriber at the calling substation A depresses the ringing key BK. Should the subscriber at the substation C be busy as a calling line, its associated relay CL would be energized, and the ground through its alternate contact 9 would be connected to the common conductor 50, or, if the line is busy as a called line, there will be ground upon conductor 50 through the relay TE of the subscribers line calling the said called line C, and when the subscriber at the substation A depresses the ringing key RK, he brings about the de-energization of the relay LR as above described, and the ground extending from normal con tact 58 of the relay LR over conductor 57, through normal contact 56 of the relay 12, over conductor 55 through the winding of the test relay TE, over conductor 54, through normal contact 53 of the relay CR, over conductor 52 through alternate contact 51 of the relay CR, extends over the common conductor 50 to the ground placed upon the common conductor 50 associated with the busy line C. This ground to ground connection through the winding of the test relay TE permits relay TE to remain at normal, and a busy signal is transmitted to the calling subscriber at the substation A which may be traced from the busy signal apparatus BB through normal contact of the relay TE, conductor 91, normal contact 92 of the relay LR, the normal contact 3 of the cut off relay CO, through the substation to ground.

The subscriber at the substation A receiving the busy signal knows that the called subscriber at C is busy, and he now replaces his receiver upon the switchhook, allowing the line relays LR and LE to restore. The relay LR restoring in turn opens the energizing circuit of the relay CL, and the relay CL de-energizing opens the circuit of the relay CR at alternate contact 32 of the relay CL.

The operation of the cut off relay CC associated with the calling line A will be effected, when said line A is selected and connected as a called line, in the same identical manner and over a circuit similar to that as described in connection with the operation of the cut off relay C0 of the called line C as is fully described in detail in the foregoing specification.

Should the subscriber depress his ringing key BK after sending the required impulses to connect to the called line, he fails to energize the test relay TE, as before described, and the relay TE remaining at normal no energizing circuit is established for the link connecting relay LC and the ringing control relay RC, thus preventing ringing current from being transmitted. to the encountered busy line.

The apparatus used in attempting 'to establish a connection with the busy substation C is now at normal and available for use in establishing other connections.

While I have illustrated and described a specific form of my invention, it is to' be understood that my invention may be modified and changed by those skilled in the art without departing from the broad scope of my invention. I therefore do not wish to be limited to the exact structure as shown, but aim to cover all such changes and modifications as come within the spirit and scope of the appended claims.

Having described my invention what I claim as new and desire to secure by Letters Patent is:

1. A telephone system including a calling telephone line, called telephone lines, an automatic selector switch provided with a series of relays, an impulsing circuit for energizing said relays in succession, means for maintaining the last relay energized and for de-energizing the previously energized relays of the series to extend said calling line to one of said called telephone lines, ringing means, and means controlled solely over the calling line for connecting and disconnecting said ringing means to and from the connected to called line if said line is idle to signal the subscriber thereon.

2. A telephone system including a calling telephone line, called telephone lines, a selector switch having a series of connecting relays, a plurality of lines selectable by said relays, an impulsing circuit for energizing the relays in succession, means operable subsequently for maintaining the last relay of the series energized to select the desired line and for (ls-energizing the previously energized relays of the series to extend said calling line to one of said called telephone lines, ringing means, and means controlled solely over the calling line for connecting and disconnecting said ringing means to and from the connected to called line if said line is idle, to signal the subscriber thereon.

'3. A telephone system including a selector switch having a series of relays, a plurality of lines selectable by said relays, an impulsing circuit for energizingthe relays in succession, means for maintaining the last relay of the series energized to select the desired line and for de-energizing the previously energized relays of the series, busy signaling means, automatic testing means for connecting a callingsubscribers line with the said selected desired line if said last line is idle, and to connect said busy signaling means in a circuit with the calling line if said selected. desired line is busy.

4. A telephone system including a selec-.

t W t h ha g as r-i of r ys a P1 1- said desired line is busy.

5. A telephone system including a series of relavs controlled over the calling subscribers line, called lines adapted to be" selected by said relays, and impulsingcircuit for energizing the relays in succession, a holding circuit operable to maintain the operated relays energized while impulses are being transmitted over the impulsing circuit, means for thereafter maintaining'only the last relay operated of the series in its energized position to connect with the desired line while the other relays of the series are returned to their de-energized position, busy back means, and means for automatically connecting said busy back means in circuit with the calling line if said desired line is busy.

6. A telephone system including a series of relays, lines adapted to be selected .by said relays, an impulsing circuit for energizing the relays in succession, a holding circuit operable to maintain the operated relays energized while impulses are being transmitted over the impulsing circuit, means for thereafter maintaining only the last relay operated of the series in its energized position to connect With-the desired line while the other relays of the series are returned to their dc-energized position, and means for signaling the desired line if- .it is idle, or for transmitting a busy signal to the calling line if the desired line is busy.

7. A telephone system including a calling subscriber s line and a plurality of called subscribers lines, a selector switch having a series of relays, an impulsing circuit for energizing the relays in succession, means for de-energizing all of the relays of the series that ha-vebeen operated except the last one, said last relav remaining energized to connect the calling subseribers line with the called subscribers line, ringing current means, and means controlled solelyover the calling line for connecting and disconnectmg said ringing current means-to and train the called line for signaling the subscriber thereon. I

8. A telephone system including a selector switching having a series of pairs of relays for connecting to desired lines, each Pair if ays nsensus a screwin -re lay and an auxiliary relay, an impulsing circuit for energizing the connecting relays in succession, means controlled by said auxiliary relays for switching the impulsing circuit from one connecting relay to another, means operable at the end oi the series of impulses for de-energizing all of the connecting relays operable except the last one of which remains energized to extend the connection to the desired line, ringing current means, and means controlled solely over the calling line for connecting and disconnecting said ringing current means to and from the called line for signaling the subscriber thereon.

9. A telephone system having a selector switch provided with a series of connecting relays, an impulsing circuit for energizing the connecting relays in succession, circuits controlled by the suceeding relays for opening the circuits of previously operated connecting relays, maintaining circuits for holding the operated connecting relays en ergized, means for de-energizing all but the last operated connecting relay to extend the connection to the desired line, and test means for permitting the signalling of the subscriber on said desired line if it is idle or for transmitting a busy signal to the calling line if the desired line is busy.

-10. A telephone system having a selector switch provided with a series of connecting relays, an impulsing circuit for successively energizing said connecting relays, intercon necting circuits whereby the operation of a succeeding relay opens the circuit of an operated preceding relay, holding circuits for maintaining the operated connecting relays energized during the time that impulses are being transmitted over the impulsing circuit, automatic means for maintaining energized the last operated connecting relay and for tie-energizing the preceding operated connecting relays to extend the connection to the desired line, and test means for permitting the signalling ot the subscriber on said desired line it it is idle or for transmitting a busy signal to the calling line it the desired line is busy.

11. A telephone system having a selector switch provided with a series of relays, an im'pulsing circuit for successively energizing said relays, interconnecting circuits whereby the operation 01 a succeeding relay opens the circuit of an operated preceding relay, holding circuits for maintaining the operated relays energized during the time that impulses are being transmitted over the impulsing circuit, automatic means for maintaining energized the last operated relay and for deenergizing the preceding operated relays, a calling telephone, called telephone lines, means controlled by said relays for connecting said calling telephone line to a desired one of said called telephone lines, and test means for signalling the subscriber on said desired line if it is idle or for transmitting a busy signal to the calling line if the desired line is busy.

12. A telephone system having a selector switch provided with a series of relays, an impulsing circuit for successively energizing said relays, interconnecting circuits whereby the operation of a succeeding relay opens the circuit of an operated preceding relay, holding circuits for maintaining the operated relays energized during the time that impulses are being transmitted over the impulsing circuit, automatic means maintaining energized the last operated relay and for de-energizing the preceding operated relays, a calling telephone line, called telephone lines, means controlled by said relays for connecting said calling telephone line to a desired one of said called telephone lines, and means for signaling the desired called line if the said line is idle, or for transmitting a busy signal to said calling line if said called line is busy.

18. A telephone system including a series of switching relays, a plurality of telephone lines, a pair of line relays for successively operating saiid switching relays for estab lishing a connection with any one of said telephone lines, means for causing the deenergization of one of said line relays for connecting ringing current to a connected to telephone line it the said line is idle, or to connect to a busy back signal if the said telephone line is busy.

14. A telephone system including a calling subscribefis line and a plurality of called subscribers lines, a selector switch including a series of switching relays, a pair or line relays in series with said calling line for causing the successive operation of said switching relays for interconnecting said calling line with any one of said called linesv to the exclusion of? the other of said called lines.

15. A telephone system including a calling sul'istation and. a plurality of called substations, a pair of line relays adapted to be operated at said calling substation, a series of switching relays adapted to be successively operated by said line relays to interconnect said calling substation and one of said called substations, calling substations means for applying ringing current to said called substations if idle, and for connecting a busy back signal in circuit with said calling substation it said called substation is busy.

16. A, telephone system including a selector switch having a series of connecting relays, a calling subscribers line and a plurality of called subscribers lines, a pair of line relays controlled over said calling line and adapted to transmit impulse currentt o said connecting relays whereby said connecting for Q n mi) relays energizes successivelyduring the sending of impulses to select one of said called lines, the last connecting relay to energize remaining operated to connect said calling line and the selected called line in circuitwhile the previously energized connecting relays restore to normal.

17. A telephone systemincluding a selector switch having a series or relays, a calling line and a plurality of lines selectable by said relays, means'for operating said relays in rotation and means for maintaining the last relay of the series operated to select and connect the desired called line in circuit with said called line and for de-energizing the previously energized relays of the series, automatic test means, and means for operating said test means it the selected line is idle to apply ringing current to said selected line, said test means not being afi'ected by said last means it said selected line is busy whereby a busy signal is transmitted to said calling line.

18. A telephone system including a calling line and a plurality of called lines, a series of connecting relays for interconnecting said calling line and one of said called lines, a pair of line relays for transmitting an impluse current to energize said switching relays in rotation to select one of said called lines, means for maintaining the last relay of the series energized and for de-energizing the previously energized relays of the series, means for de-energizing one of said line relays whereby means are operated to signal the selected line if idle and to connect busy signal to said calling line it said selected line is busy.

19. A telephone system including a se lec-tor switch having a group of relays in series, a plurality of lines selectable by said relays, means for energizing said relays in rotation, the. second relay energizing opens the holding circuit for the first energized relay, the third relay energizing opens the holding circuit for said second relay, etc, means for maintaining the relay of the series last to energize operated to select one of said lines, and automatic test means for connecting a calling line with said selected line it said selected line is idle.

20. A telephone system including a select-or switch having a series of pairs of relays. each pair of relays comprising a connecting relay and an auxiliary relay, a calling line. a plurality of called lines adapted to be selected by said pairs of relays, means for transmitting a number of current impulses to energize a number of said pairs of relays, the number of pairs of relays energized being the same as the number of impulses transmitted, means for maintaining the last pair of said switching relays energized operated to select one of said called 'lc'cted by said relays, a calling line'and means controlled over said calling line for operating the relays of the series in rotation, means for maintaining the last operated re lay of the series energized to select one of said called lines, and for restoring the pre riously'operated relays of the series, test means, other means for effecting said first means to cause the operation of said test' means to connect said selected called line in circuit with said calling line if said called lineis idle. and to connect ringing means to said called line.

Atelephone system including a calling subscribers line and a plurality of called SE-rOSCI'llJCIS lines, a selector switch having a series of relays, an impulse circuit tor energizing the relays in, succession, means for (lo-energizing all ofthe relays of the" series that havebeen operated exceptthe last one, said last relay remaining energized to connect the calling subscribers line with the called subscribers line, means for ri'n ing the called subscriber, and .means i or autoniatically disconnecting ringing currentfrom the called subscribers line.

A telephone system including a series of relays, a calling line, a plurality of selectable called lines adapted to be selected by said switching relays, impulse means for successively energizing said relays, means for maintaining the last energized lay of the series operated to select one of said called lines while the previously energized relay the series returns to normal, automatic testmeans for interconnecting said calling line and said selected line, and for connecting ringing means to said called line it said selected line is idle and for preventing the interruption of and the application of ringing current to said selected line it busy, and means for rendering said calling line and said selected line busy when said lines are in use.

24. A telephone system including a selector switch having a series of connecting relays, a. pair of line relays and a pair of slow-acting relays, one of said line relays controlling the circuits of said pair of slowacting relays, subscriber controlled means for operating said pair of line relays to transmit impulses of current to energize said connecting relays in rotation. means for maintaining the succeeding energized relay of sa d series operated and to de-energize the preceding energized relay.

25.,A telephone system including a callto energize said switching relays in rotation,

means for maintaining said last relay of the series operated to select one of said called lines and to de-energize the preceding energized relay of the series, means for de-energizing one of said line relays, a test relay for connecting said calling line and said selected line and operable upon the de-energization of said line relay providing said selected line is idle.

26. A telephone system including a call ing line and a plurality of selectable called lines, a series of counting relays adapted to select one of said called lines, a pair of line relays and a pair of slow acting relays, one of said line relays controlling the circuits of said slow acting relays, means controlled over said calling line for operating said line relays to transmit current impulses to energize said counting relays in rotation, means for maintaining the said last relay of the series operated to select one of said called lines and to deenergize the preceding energized relay of the series, means for de-energizing one of said line relays, a test relay tor connecting said calling line and said se lected line and operable upon the de-energization of said line relay providing said selected line is idle, and means for preventing the operation of said test means when said line relay is deenergized if said selected line is busy, to connect busy signal to said calling line.

27. A telephone system including a calling line and a plurality of selectable called lines, a series: of counting relays adapted to select one of said called lines, a pair of line relays and a pair of slow-acting relays, one of said. line relays controlling the circuits of said slow acting relays, means controlled over said calling lines for operating said line relays to transmit current impulses to energize said counting relays in rotation, means for maintaining said last relay of the series operated to select one of said called lines and to de-energize the preceding energized relay of the series, means for de-energizing one of said line relays, a test relay for connecting said calling line and said selected line and operable upon the de-energization of said line relay providing said selected line is idle, said test means When operated also connecting ringing means to said selected line.

Signed by me at Chicago, in the county of Cook and State of Illinois, this 7 day of September, 1921.

GEORGE A. YANOCHOWSKI. 

